1) Field of the Disclosure
The disclosure relates generally to assemblies and methods for rotorcraft, and more particularly, to assemblies and methods for counter-torque control for rotorcraft such as helicopters.
2) Description of Related Art
Rotorcraft or rotary aircraft, such as helicopters, are versatile vehicles for transporting supplies, passengers and cargo over moderate distances at relatively high speeds. They are capable of vertical lift and forward propulsion without the need of a runway, unlike most other passenger and cargo transporting style aircraft, such as propeller-style airplanes and jet aircraft with a main fixed aircraft lifting wing.
Such rotorcraft or rotary aircraft typically fly by means of thrust created by rotation of a main rotor having blades or rotor/wings driven by a rotating shaft that rotates about a generally vertical axis above the airframe of the rotorcraft. When the main rotor rotates, a torque is produced that must be counteracted by a counter-torque that opposes and compensates for the torque of the main rotor to prevent the main rotor turning in one direction and the rotorcraft airframe turning in an opposite direction.
Known solutions exist for counteracting the torque produced by the main rotor. For example, in a rotorcraft having a single main rotor, counter-torque and directional control may be achieved by mounting a tail rotor having smaller rotor blades on the rotorcraft tail. The tail rotor rotates about a generally horizontal axis and produces a sideways thrust that prevents the rotorcraft airframe from rotating. However, due to location and exposure of the tail rotor, during rotation, the tail rotor may be susceptible to tail rotor strikes against various objects or surfaces if the tail rotor inadvertently gets too close and makes contact with such objects and surfaces. In addition, due to the tail rotor being exposed, rotorcraft aerodynamic performance may be compromised. Moreover, tail rotors may produce a considerable amount of noise during rotation.
In addition, known solutions requiring no tail rotor exist for counteracting the torque produced by the main rotor. For example, rotorcraft exist having two main rotors that turn in opposite, or counter-rotating, directions. Because each main rotor neutralizes or cancels the torque produced by the other main rotor, no tail rotor is needed in this type of rotorcraft. Such rotorcraft may include, for example, rotorcraft with a coaxial rotor design having one main rotor located on top of the other main rotor, rotorcraft with a twin-rotor or tandem rotor design having one main rotor located side-by-side to the other main rotor, rotorcraft with a tiltrotor design having helicopter-like rotors attached at wingtips, and rotorcraft with a twin-rotor synchropter design having one main rotor that meshes into another main rotor like a gearwheel. However, due to both main rotors being exposed, the rotorcraft aerodynamic performance of such rotorcraft designs may be compromised. Moreover, the two main rotor blades of such known rotorcraft may produce a considerable amount of noise during rotation.
Accordingly, there is a need in the art for improved rotorcraft assemblies and methods that require no tail rotor, that counteract the torque produced by the main rotor, and that provide advantages over known assemblies and methods.